Array.prototype.copy

[Sunny]

Array.prototype.copy = function () {
    return [...this, ...this]
}
console.log([1, 2, 3, 4, 5].copy());

[kangkang123269]

Array.prototype.copy = function() {
  var len = this.length;
  var arrCopy = new Array(len);
  for (var i = 0; i < len; i++) {
    arrCopy[i] = this[i];
  }
  return arrCopy;
};